Southern Ocean Tutorial

I can’t take my eyes off the Vendee Globe, that solo, non-stop, around-the-world race whose fleet of rocket ships launched some 51 days ago.

The first weeks of flying down the Atlantic were interesting enough (it’s been a year of record times), but only as the boats encountered the difficulties of the Southern Ocean did my interest become acute.

At this point in the Figure 8 project, I am focused on spreadsheets and such sexy activities as rebuilding bilge pumps. But when there is a spare moment, I am glued to the Vendee Globe, because for me it’s an opportunity to watch as skippers wrestle with the same big weather and big ocean I’ll encounter there next year.

By way of reminder, Tony owned Moli (then Toanui) from 1996 to 2013. In 2002-2003, Tony completed a 177-day, 25,000-mile, non-stop circumnavigation via the Southern Ocean, something no one from North America had done to that point, and I was fortunate he had traveled to San Francisco to inspect Mo and review the Figure 8 with me.

My plan for the south had been simple: keep the boat as far north as possible in order to maintain access to good, or at least less tremendously bad, weather. Thus, after rounding the Horn at 56S, my theoretical route took me quickly back up to 40S, where it remained until Australia and New Zealand forced it back down to 45S. This was based loosely on Moitessier’s experiences as described in The Long Way, and though clearly conservative, I thought it justified given that Motessier’s own chart notes referenced several bracing events like “strong SW gales, keel in the air.”

But Tony disagreed with this approach.

After dinner, he drew a low-pressure system on a paper towel and placed it atop an Antarctic chart I’d pulled from the closet, and the lesson in tactics commenced.

It went like this…

If the goal is to pass through that cold, hard ocean as quickly as possible, said Tony, one must go south, far south. This has the effect of both shortening the total distance around the circle and putting the yacht into consistently stronger winds.

For example, in 2002 Tony had intended to remain at roughly 44S for his circuit around Antarctica,

[but] the lows seemed to be tracking along between 50 and 55S, so I stayed along latitude 47S for … 7 weeks, using the weatherfaxes from Chile, South Africa and then Australia to monitor [their] progress. … Most of the time the wind oscillated from NW to SW, usually Force 6-7 occasionally Force 8 or 9. (source: Tony’s passage summary)

This move took 1500 miles off the loop and increased Taonui’s speed to an average of 152 miles a day (this up from a total course average of 137 miles a day).

But southing has its limits, continued Tony, and one of the bounding factors is the usual NW to SE to E trajectory of low-pressure systems. Remembering that below the equator these systems have a clockwise rotation, it is easy to see that for a vessel on an easterly course, staying above the lows keeps wind in that desirable quadrant–aft of the beam–and falling below them creates potentially dangerous headwinds.

The other bounding factor is ice, specifically icebergs that calve regularly from Antarctica and can migrate a great distance north before dissipating. Luckily, while ice danger cannot be overstated, its summer-season limits are generally known and charted.

Ice Limits Chart from the Admiralty Antarctic Pilot. Best to stay above the blue line.

It all sounds simple enough when being discussed over the dinner table and in the comfort of one’s home.

It’s not simple.

With no land masses to impede their progress, Southern Ocean winds are not just stronger than in other oceans, they are far more variable. Low-pressure systems, that area’s defining feature, are typically compact, powerful, and fast-moving; they bring frequent, blasting squalls and kick up thick cross seas, and as Warwick Thompkins attests (repeatedly) in 50 South to 50 South, a boat can be rolling on a windless sea one minute and battling a brutal storm the next.

Skip forward two months and I’m watching these tactics and their complications play out among the professional sailors of the Vendee Globe.

The eighth Vendée Globe, which launched on November 6 from Les Sables d’Olonn, France, is the only non-stop, solo, around-the-world race via the Southern Ocean without assistance. Some of the twenty-nine skippers representing four continents and ten nations are chasing the record time of 78 days established by François Gabart in 2013; others are attempting simply to survive the grueling course. By way of testament to the race’s difficulties, to date, a full third of the boats that crossed the starting line have been forced to retire due to keel damage, rudder damage, or collapsed rigs. All but two of these disasters occurred after the fleet passed Cape of Good Hope.

The boats, 60-foot sleds, are “among the fastest modern racing monohulls. Built using composite materials, they are designed to be as light as possible (approx 7.5 tons) while at the same time being solid enough to withstand the worst conditions one can find when racing (at 20 – 25 knots) on the open seas.”* Compare my boat: at 45-feet, nearly 20 tons, and averaging 7 – 8 knots, Moli is 33% shorter, 1.8 times heavier and generates less than a third the speed (I’m not complaining, mind you). Where the Vendee Globe is concerned, fast and light seem understatements.

Banque Populaire, an IMOCA 60 currently leading the pack, is pictured here attempting to blast out of earth’s orbit. (Photo Credit: Vendee Globe)

What does Southern Ocean weather look like for these skippers? Here are three graphical examples:

This shot of Antarctica and the surrounding Southern Ocean is from Windytv (windytv.com). The streams you see are the wind patterns from day 36 of the race. Darker colors are stronger winds (see scale at right for knots). Note the low-pressure system at the top of the chart is producing surface wind speeds (not including gusts) of 40 knots and more. At the time of this snapshot, most of the Vendee fleet was struggling inside the purple tongue at left and below Australia.

Here is a perfect (and typical) example of the weather tactics Tony outlined. In this snapshot from day 42 of the race, we see the Vendee fleet (colored triangles) spread out south and west of Australia. Near the bottom of the chart are three lows (“L”) marching east, the most eastward of which is quite intense. The orange area containing two of the lows is called “the exclusion zone” and is off limits to racers due to increasing ice-impact danger there. Note that the boats in the middle of the pack are stacked up just above the exclusion zone and on top of the passing lows, which is to say, most are as far south as they dare.

But it is not always possible to stay above the lows, as exemplified in this snapshot from day 47 of the race. Note that in his approach to Cape Horn, Alex Thomson on Hugo Boss (black triangle) has gotten caught under of a low and has tacked due south in order to manage strong headwinds. Unless the low passes quickly, he may be required to tack north in order to avoid the exclusion zone.

Of all the Vendee skippers, I’ve tended to follow most closely the sole American, Rich Wilson on Great American IV and the sole Brit, Alex Thompson on Hugo Boss.

Both skippers are posting frequent, gripping video logs, only two of which are below. Rich Wilson, currently in a very respectable ninth place, is 65 years of age and the oldest Vendee Globe participant. His logs tend to be detailed and instructional, like this video discussing the dynamics of catching up to a storm…

Alex Thomson’s videos are more experiential. Alex carried a commanding lead early and before his starboard foil was knocked away. Still solidly in second, Alex continues to post sobering video logs like this one from December 9th. Alex is a bull of a man and his reports tend to be upbeat, but note here that fatigue and emotional strain are clearly evident…

Two more from Alex where he discusses both weather tactics and the difficulties of maintaining himself and the boat: here and here.